The present invention relates to a cigarette-making machine.
In particular, the present invention relates to a cigarette-making machine having an input chamber from which the shredded tobacco is taken by a carding unit to be supplied to a descending shaft. At the lower end of this latter there is located a supply conveyor which conveys the tobacco towards the lower end of an ascending output shaft.
In general, the said descending shaft serves as an accumulation magazine in that, within it, there is constantly present a column of tobacco from the lower end of which the tobacco itself is continuously taken by a toothed roller which feeds it over the said conveyor.
In the known cigarette-making machine as described above, the upper surface of the said tobacco column is not normally a flat surface because of the fact that the said carding unit supplies the tobacco to the interior of the descending shaft in an imperfectly uniform manner over the whole of the width of the descending shaft itself.
Such non-uniformity involves significant disadvantages in that they cause non-uniformities in the carpet of tabacco formed by the said toothed roller on the said conveyor and, therefore, non uniformity in the distribution of tobacco along the continuous rod of cigarette which is formed at the output of the said rising shaft.
For the purpose of eliminating such disadvantages it is known to provide within the descending shaft a plurality of level indicators distributed over the width of the shaft itself and operable to detect the level reached by the tobacco at several points across the top of the said column. The signals emitted by these level indicators are used to correct the distribution of the tobacco taken from the carding unit. In particular, one known method of correction consists in taking off, by means of rotary take-off elements, quantities of tobacco determined across the width of the carding unit in such a way that these latter supply less tobacco to the zones of the descending shaft in which the level of the tobacco is greater. Another method of correction lies in achieving a similar result by separating the carding unit into a plurality of sub-units disposed alongside one another across the width of the descending shaft, and in selectively adjusting their speed of supply in response to the signals received by the said level indicators.
From what has been described above it is clear that the known methods of correction described require, for their performance, extremely complicated mechanical devices which, as well as rendering the cigarette-making machine extremely expensive, drastically reduce the reliability thereof.